Valve for percussive tools



W. A. SMITH.

VALV E FOR PERCUSSIVE TOOLS. APPLICATION FILED OCT. 25, 1919.

1 ,350, 342, Patented Aug. 24, 1920.

2 SHEETS-SHEET l. 5 17 1 8 ]6 [21 18 Rama 4 4 w f x fi W. A. SMITH.

VALVE FOR PERCUSSIVE TOOLS.

APPLICATION FILED OCT. 25,1919.

1 ,350, 342. Patented Allg- 24, 1920.

2 SHEETSSHEET 2. 14

INVENTOR.

UNITED STA, EsrAr-ENT OFFICE.

WILLIAM A. smn'n, or EASTON, P NNSYLVANIA, 'ro INGERSOLLPRAND COMPANY,or masnx CITY, NEW JERSEY, A'conrokA'rIoN 01 NEW JERSEY.

vALvL FOR rnnoussrvn mooLs.

To all whom it may concern:

Be it known that I, WILLIAM A. SMITH,

a citizen of the United States, residingat Easton, in the county ofNorthampton and State of Pennsylvania, have invented a certain new anduseful Improvement in Valves for Percussive Tools, of which thefollowing is a specification.

This invention relates to a fluid operated percussive tool, and inparticular tov a percussive tool of the diii'erential piston type havinga valve for distributing fluid pressure to some parts of the cylinder tooperate the piston or hammer.

The objects of the present invention are to provide a differentialpiston percussive tool with a very simple form of piston having twopressure areas to force it in one direction and one pressure area'toforce it in the opposite direction.

. Another object of the invention is to provide a percussive tool of thehammer type with a fluid distributing valve which will control theadmission of fluid to one end-of the piston cylinder and will alsocontrol the exhaust of a part of the fluid from both ends of thecylinder.

A further object of the invention is to provide a percussive tool with asimple form of valve which may be conveniently located at one side ofthe cylinder in a compact and easily accessible position.

A further object of the invention is to construct the valve so that itwill operate quickly and sensitively in order that the number of blowsof the piston may be as great as possible.

With these and other objects in view my invention consists in thefeatures of construction and operation set forth in the followingspecification.

In the drawings annexed hereto and forming a part of this specification;

igure 1 shows a longitudinal sectionalview ofthe valve and a part of thevalve chest and cylinder.

Fig. 2 a longitudinal view of'the complete tool in section with thepiston and valve in one operative position.

' Fig. 3, a view similar to Fig. 2 with the piston and valve in anotheroperative position.

Fig. 4, a longitudinal view in section of a slightly modified form ofthe invention.

Specification of Letters Patent.

Patented Aug. 24, 1920.

Application filed October 25, 1919. Serial No. 838,882.

Figs. 5 and 6, views similar to Fig. 4 with thepiston and valve indifferent operative POSItlOIlS.

Referring now more particularly to Figs. 1-2-3 of the drawing, thecylinder of the percussive tool is shown at 1, having a large bore 2 anda small bore 3 in which reciprocates a piston 4. Piston 4 is providedwith a head 5 adapted to slide in the forward bore 2 of the cylinder andalso a shank 6 fitting the small bore 3. Preferably the piston is madewith a symmetrical shank 6 extending forwardly from the piston head 5.,of the same diameter and length as the shank 6. This forward shank 6 ofthe piston fits within the chuck 7, in the forward end of which fits thedrill steel or other percussive implement 8. The chuck 7 and cylinder 1are adapted to be held rigidly together by any suitable means not shown.

From the above description-it will be seen that, a constructionis'provided which will- .permit the piston 4 to be reversed upon itselfwhen one end becomes damaged or broken.

At the rear end of the cylinderl is provi ed a fluid cavity 9communicating by a port 10 with an inlet of any type adapted to supplymotive fluid to the drill from any suitable source. The cavity 9 is oflarger diameter than the small bore 3 so that pressure is continuallyexerted atia constant pressure against the rear face of the piston shank6, thus forcing it at all timestoward the forward end of its stroke. thestroke of the piston 4 a conduit 12 is provided which is opened at ornear the forspaced somewhat from the head 15 by a- .neck portion 17, andat the rear end of the valve 14 a head 18 is provided slightly smallerin diameter than heads 15 and 16. Extending continuously from end to endof the valve 14 is a leak port 19 which'intercepts a short leak port 20in the neck por- To reverse tion 21 of the valve 14, which, during the oeration of the tool is continuously supplied with fluid at constantpressure from conduit 22.

With the piston'in the above position as shown in Fig. 2 it is about tostart upon its forward stroke and the valve 14 is already moved to itsforemost position, enabling fluid pressure to be supplied to port 22which is in communication with the pressure cavity 9, past the neck 21of the valve 14 and into the rearward part of the cylinder bore 2through the port 23. Pressure exerted upon both of the rearward pressureareas of the piston thus forces it forwardl to the position shown inFig. 3, by whic time the piston has passed the central exhaust port 13,thus allowing the'fluid pressure in rear of the cylinder bore 2 toescape and has opened communication by means of the conduit 12 from thepressure cavit 9 to the forward end of bore 2, so that orward pressureon the rearward face of the shank 6 is resisted by full pressure upon apressure area on, the front face of the head 5.

During the forward stroke of the piston 4 after passing the centralexhaust port 13 pressure in advance of the piston head 5 continues to beexhausted from the forward end of bore 2 through port 24, until thisport is overrun by the piston, after which time the ressure begins tobuild up'in advance 6f the piston head 5. This increased pressurecombined with the pressure supplied in advance of the head 15 of valve14 through the conduit 19 forces the valve 14 to its rearmost positionas indicated in Fig. 3. This movement of the valve 14 closes theauxiliary exhaust port 24 near the forward end of the bore 2 andsimultaneously closes the admission port 23 at the rear end of bore 2.The-piston 4 is now ready. to make its return stroke which it is enabledto do by means of the pressure in advance of the head supplied throughconduit 12. In order to continue the exhaust of fluid pressure from therear end of bore 2 after the central exhaust port 13 closes anotherauxiliary exhaust port 26 is provided opened by the rearward movement ofthe valve 14.

It will be noted that the valve 14 is constantly urged toward itsforward position b a constant pressure exerted on this valve. 'I hispressure area is represented by the difference in areas between the rearof head 16 and head 18 of the valve. The valve is enabled to move to itsrear position by pressure in advance of the head 15 overcoming thisslight forwardly exerted constant pressure. Throughout the operation ofthe tool fluid passes into the leak port 19 by means of port 20 which isalways open to pressure from chamber 9 and conduit 22.

With the valve in the position of Fig. 2,

zming of the valve.

for instance, after port 24 is closed by the' to throw the valve pastthe port 25 is thus built up due to fluid passing through passa e 19 andto leakage around the valve.

y means of this supply of fluid to both ends of valve 14 the cushioningchamber at the extreme ends of the valve chest is being continuallysupplied with fluid thus increasing the cushionm of the 'valve at eitherend of its stroke an aidin materially in its quickness of action am?preventing slam- The above described construction gives a i very quickactin valve, enabling the piston to make a rapi striking blow which willbe practically uncushioned until it is about to strike the drill steel8.

The rearward movement of the valve 14 is begun by means of the leakagementioned and the pressure supplied through leak port 19 and 1scompleted as soon as the valve moves slightly past port 25. As soon asthe piston 5 moves rearwardly sufliciently to uncover the centralexhaust port 13 the pressure at the forward end of valve 14 drops thuspermittin the constant pressure forcing the valve orward to throw thevalve forwardly again.

Referring now to Figs. 45 and 6, a differentmethod of operating thevalve 14 is shown. This comprises a small conduit 30 extending froma'portion of the small bore 3 of the cylinder 1 at a point overrun bythe shank 6 toward the end of the forward stroke of the piston andopening at its other end into the valve chest in advance of the valvehead 15 as shown at 31*. With this method of reversing the movement ofthe valve 14 the pressure is supplied from a constant pressure sourcecomprising one of the cylinder chambers overrun by the piston during aportion of its stroke, and is independent of the amount of fluidcushioned in advance of the piston head 5 at the very end of the pistonstroke. Furthermore the position of the orifice 31 of this conduit 30may be accurately determined so that the valve will be thrown at adefinite and accurately determined point in the stroke of the pistonwhile in the modification shown in Figs. 1-2 and 3 the point at whichthe valve 14 may be thrown might vary due'to the difference in pressureat either end of the valve 14 at different times due to the leako theforward end of the cylinder bore 2.

The valve 14 in this modification of the invention is constantly forcedto its forward position in the same manner as the modificaa e of fluidpassing the valve heads or out .versing the movement of soon as piston 5moves tion shown in Figs. 1-2-3, and also 0 erates the auxiliary exhaustports 23 an; 24 in the same manner.

31 is overrun by the piston shank 6 during the forward stroke of thepiston which'occurs toward the end of that stroke, fluid passes throughconduit 30 to the port 31 and forces the valve to its rearward position.Almost simultaneously the shank uncovers the rear port of conduit 12thus rethe piston 5. As far enough on its rear stroke, port 25 isoverrun by head 5 so that the fluid supplied through port 12 isaugmented by fluid through conduit 30. Continued movement of piston 5uncovers port 33 which intercepts and forms an additional openingforconduit 30 so that as soon as this port}- is opened this port may conveyfluid to the forward end of bore 2. As soon asthe piston overruns thecentral exhaust port 13 pressure is exhausted from conduit 30 and'theforward end of the valve chest through port 33, thus enabling the valve14 to'again move forwardly.

The valve 14 shown in Figs. 4-5 and 6 moreover is made solid, that is,without the provision of the leak port extending from end to end. of thevalve.

In other respects the construction and operation of the tool shown inFigs. 15 and 6 is similar in every way to that shown in Figs. 1-2 and 3.

It is to be understood that the present showing and description discloseonly one specific embodiment of my present invention, and that otherforms and modifications are included within the spirit and scopethereof, as expressed in the appended claims.

' cylinder and a plurality of auxiliary exhaust 1. In a percussive tool,a valve chest, a valve adapted to operate therein, a head at one end ofsaid valve controlling an auxiliary exhaust port, a head intermediatethe ends of the valve controlling an admission port and an auxiliaryexhaust port, said valve being forced in one direction by constantpressure against one end face and thrown to its opposite position by afluctuating pressure against an opposite end face.

2. In a percussive tool, a valve chest, a valve adapted to operatetherein, a head at one end of said valve controlling an auxiliaryexhaust port near one end of the cylinder, a head intermediate the endsof said valve controlling an admission port and an auxiliary exhaustport near the opposite end of said cylinder, said valve being forced inone direction by constant pressure against one end face and thrown toits opposite position As soon as the port ating within said by afluctuating pressure against an opposite end face.

. 3. In a percussive tool, a cylinder, a piston therein, and a valvechest provided with an admission port intercepting one end of. thecylinder, and a pluralit haust ports from said cylinder, a valveopervalve chest, said valve provided .with a head controlling anauxillary exhaust port and another head controlling an admission port toa cylinder pressure chamber and another auxiliary exhaust port, a thirdhead provided on said valve of smaller diameter than the first mentionedheads, a conduit extending from a constant pressure chamber of saidcylinder to one end of the valve, whereby fluld may be supplied to oneend of the valve chest to throw the valve in one direction.

4. In a percussive tool, a cylinder, 9. piston therein, and a valvechest provided with an admission port intercepting one end of thecylinder and a plurality of auxiliary exhaust ports from said cylinder,a valve operating within said valve chest, said valve provided with ahead controlling an auxiliary exhaust port and another head controllingan admission port to a cylinder pressure chamber and and anotherauxiliary port,-a third head provided on said valve of smaller diameterthan the first mentioned heads, a conduit extending from a constantpressure "chamber of said cylinder and overrun by said piston near oneend of its stroke, whereby fluid may be supplied to one end of the valvechest to throw the valve in one direction.

5. In a percussive tool, a cylinder, a piston therein, and a valve chestprovided with an admission port'intercepting one end of the ports fromsaid cylinder, a valve operating within said valve chest, said valveprovided with a head controlling an auxiliaryexhaust port and anotherhead controlling an admission port to a cylinder pressure chamber andanother auxiliary port, a third head provided on said valve of smallerdiameter than of auxiliary exthe first mentioned head, a conduit extend-I ing from a constant pressure chamber of said cylinder and overrun bysaid piston near one end of its stroke, said conduit hav ing a portintercepting and overrun by the piston head to permit an exhaust offluid.

from the forward bore of the cylinder during a portion of the rearwardstroke of the piston, to allow the valve to return to its forwardposition.

In testimony whereof I have hereunto set my hand.

7 WILLIAM A. SMITH.

